In IV-line blood draws, what is the purpose of using a discard tube and what volume is typically discarded?

In IV-line blood draws, what is the purpose of using a discard tube and what volume is typically discarded?

• A. To prime the collection syringe; discard typically 15–20 mL.
• B. To clear residual IV solution before peripheral collection; discard typically 5–10 mL or per facility policy.
• C. To calibrate the collection device; discard 0.5–1 mL.
• D. To identify sample contamination; discard 2–3 mL.

Answer: (B)

The main idea is to clear any IV fluids or medications from the line before collecting the blood so the sample reflects the patient’s blood rather than the infusion. Using a discard tube pushes out that residual solution, preventing dilution or contamination that could skew test results. Typically you’d discard about 5–10 mL, but the exact amount should follow your facility’s policy and be adjusted for the specific IV setup.

The main idea is to clear any IV fluids or medications from the line before collecting the blood so the sample reflects the patient’s blood rather than the infusion. Using a discard tube pushes out that residual solution, preventing dilution or contamination that could skew test results. Typically you’d discard about 5–10 mL, but the exact amount should follow your facility’s policy and be adjusted for the specific IV setup.